1. Field of the Invention
The present invention relates to a method of identifying a patient's urethral anatomic course which is especially suited for accurately locating a brachytherapy or cryoablation treatment element into a patient's prostate thereby allowing a practitioner to achieve optimal spacing between the treatment element and the urethra, while still effectively positioning the treatment element in effective and operative proximity to a tumor, Benign Prostatic Hyperplasia (BPH) tissue, or other desired treatment site within the prostate. In this regard, the present invention is further directed towards a urethral identification system and more specifically a urethral identification catheter which substantially enhances the identifyability of the urethral boundary at the prostate by generating, on demand, an acoustic interface that is effectively visible utilizing ultrasound equipment. As a result, utilizing the present system and method, a practitioner can take into account the possible detrimental effects of locating treatment elements, such as radioactive seeds and/or cryo-probes, too close to the urethra itself, while still appropriately positioning the treatment element to effectively treat or affect a tumor, BPH tissue or other treatment site.
2. Description of the Related Art
The prostate is a male accessory sex organ located inferior to the urinary bladder and anterior to the rectum. Roughly the size of a walnut, the prostate is located in generally close proximity to the urinary bladder and surrounds and/or encircles an upper part of the urethra, the tube that is connected to the urinary bladder and empties urine therefrom. Prostate cancer is potentially aggressive and is the second leading cause of cancer deaths among men in the United States. When diagnosed at an early, localized stage and when the disease is organ confined, prostate cancer is also often considered one of the most treatable and curable forms of cancer. As a result, early detection and effective treatment is of a critical nature.
Over the years a variety of different techniques and procedures have been developed in an effort to effectively treat prostate cancer, as well as other disorders associated with the prostate, including, but not limited to Benign Prostatic Hyperplasia (BPH). Specifically, in addition to traditional radiation/chemotherapy treatments which are commonly employed for a variety of different types of cancer, due to the localized nature of prostate cancer, if detected sufficiently early, a variety of additional techniques to treat prostate tumors have been developed.
Of the existing treatments, one procedure involves the complete removal of the prostate from the patient and/or the resection of affected portions of the prostate. Given the nature of a malignant tumor, when surgery is the elected course of treatment, complete removal of the prostate is generally undertaken. However, in many circumstances surgery for the removal of a prostate may not be desirable for a variety of reasons. Among these are the post operative risks of urinary incontinence and erectile dysfunction, and co-morbid medical conditions which may increase a patient's morbidity and/or intra-operative mortality. The anatomic location of the prostate, in relation to the external urinary sphincter and the lateral neurovascular bundles, mandates that extirpative surgical procedures for the prostate, maintain the integrity of the external urinary sphincter and preserve the neural erectile pathways. Therefore, it may be preferable to leave the prostate intact. As a result, alternative minimally invasive techniques which treat prostatic malignancies, but do not require removal of the prostate may ultimately be the preferred course of treatment, and such treatment protocols are continuously being perfected.
In particular, there exist a variety of novel techniques which do not require a patient to be subjected to excessive doses of radiation, but which perform substantially localized treatment directly to the prostate. One such technique known as transperinael interstitial brachytherapy (“brachytherapy”) is commonly utilized when managing localized prostate cancer. Specifically, brachytherapy involves the transperineal delivery of radioactive implants, sometimes referred to as seeds, into the stroma of the prostate and in substantially close proximity to the tumor, for an extended period of time. In this regard, the one or more radioactive seeds can directly and/or locally treat a malignant tumor, often ultimately destroying the tumor, with limited effects to the rest of the patient's body.
Still another technique of localized treatment of a malignant tumor in the prostate, as well as the treatment of BPH, a condition whereby prostatic hypertrophy can result in an impediment to the evacuation of urine through the urethra, involve a treatment method known as cryoablation of the prostate. Under such cryoablation techniques, one or more cryo-probes and temperature sensing probes are introduced into the prostate into operative proximity with the malignant tumor or the desired treatment site. Specifically, the cryo-probes often include small gauge needles that can be effectively inserted into the prostate from the exterior of the patient. Through these cryo-probes, a cold temperature is effectively delivered at the treatment site, such as the site of the tumor, such as through the delivery of a cryogen gas including argon gas. Once the cryogen is delivered, a field of cold temperature is generated that forms essentially an ice ball to contain a majority of the lethal portions of the tumor, and/or to shrink the prostate. Subsequently, these ice balls are allowed to thaw, and then one or more subsequent freeze/thaw cycles can be performed in an effort to effectively cure the malignancy of the tumor and/or relieve the pressure resulting from the BPH.
In addition to the above techniques for localized treatment of a tumor and/or BPH and/or other aliments of the prostate, it is also recognized that other techniques are continuously being developed, refined and/or tested in an effort to achieve directed and localized treatment of tumors or other disorders within the prostate. Generally in such techniques, and especially in the techniques of brachytherapy and cryoablation, it is of significant importance for a practitioner to obtain an effective image of the prostate in order to identify a deposit location of the treatment element, be it radioactive seeds and/or cryo-probes, without performing highly invasive procedures. Traditionally, such imaging of the prostate is achieved utilizing transrectal ultrasonography.
In particular, transrectal ultrasonography requires that a practitioner insert an ultrasound probe into the rectum, and utilizing the probe, direct ultrasound towards the prostate. When employing such an ultrasound system, the practitioner is thereby able to visualize an image of the prostate, on a monitor, in real time during the positioning of a treatment element. Unfortunately, while such techniques are generally effective for viewing the exterior shape and location of the walnut sized prostate; due to the inherent physical nature of the prostate and its circumferential orientation around the proximal urethra, practitioners typically cannot obtain any meaningful, sustained, and standardized imaging of the urethra, and more specifically the anatomic course of the prostatic urethra. There currently exist some techniques for achieving a fleeting and inconsistent viewing of the urethra. Such techniques include the manual manipulation of a Foley catheter within the urethra or the introduction of an aerated gel into the catheter. Such techniques, however, cannot be readily controlled into a standardized and manageable on and off position, and generally provide merely a temporary, variable glimpse of the urethra, if any. Furthermore, based upon the previous, traditionally accepted practice, it was not necessary for the practitioner to be able to view and/or recognize the urethral boundaries within the prostate, as the primary item of importance related to appropriate viewing of the shape, size and location of the prostate so as to effectively achieve proper positioning of the treatment element within the prostate. Also, given the general desire to minimize the potential negative impact of the treatment elements, and especially the radioactivity from the radioactive seeds on the surrounding tissue and/or organs, the treatment elements have traditionally been implanted substantially into the prostate, such that the prostate itself would act as a shield for the external tissues and/or organs.
Although such practices had been traditionally accepted, more recent studies in brachytherapy have concluded that positioning of a treatment element in substantially close proximity to the urethra, such that the urethra is exposed to higher radiation doses, can correlate with urethral toxicity. The subsequent detrimental effects to the urethra may be clinically experienced as irritative voiding symptoms, urinary retention, and/or recto-urethral fistulas. Therefore, determining the precise location for the placement of the treatment element, such as radioactive seeds, relative to the urethra, can impact the nature, location, and quantity of treatment to be employed. As a result of these discoveries, it would be highly beneficial to provide a method and system which can effectively provide for the identification of the urethral course through the prostate, thereby allowing a practitioner, in real time, to effectively identify not only the external boundaries of the prostate, but also the urethral boundary, thereby taking both boundaries into consideration when appropriately positioning a treatment element, such as radioactive seeds and/or cryo-probes. In particular, ideal techniques may call for a positioning of the treatment element in substantially close proximity to a malignant tumor, while maintaining a maximum possible spacing from the urethral boundary. As indicated, however, presently available systems and methods do not permit for the effective viewing and/or distinguishing of the urethra relative to the prostate so as to substantially aid in treatment, and no identification systems and/or techniques which provide for a clearly visible, on demand on/off, and standardized visualization are known to be implemented. As a result, the method and system of the present invention can provide a substantial enhancement in the field of art associated with localized treatment of tumors and other disorders, such as BPH, within the prostate in a manner which reduce urethral exposure to the treatment element and thereby reduce post operative complications to the urethra.